Transformer tank construction



Oct. 2, 1934. N CH LS 1,975,168

TRANSFORMER TANK CONSTRUCT ION Filed 001;. 5, 1952 wags/z LgVlL Ml/V. 0/ LEVEL Patented Oct. 2, 1934 UNITED STATES 1,975,168 TRANSFORMER TANK CONSTRUCTION Louis 0. Nichols, Wauwatosa, Wis., assignor to Allis-Chalmers Manufacturing Company, Milwaukee, Wis., a corporation of Delaware Application October 5,

Claims.

This invention relates to casings for liquid.- immersed electrical apparatus, and more particularly to casings for transformers having a gas space above the level of the insulating oil.

In large high voltage transformers having casings of conventional design and provided with a gas space above the oil there is the danger that a flash-over from the lower terminals of the high voltage bushings to the casing may occur 0 if the oil level drops below these terminals. In such transformers it is possible for the oil level in the main casing to drop enough to expose the lower terminals by reason of the contraction of the oil due to low temperature. For example, in a transformer casing 16 feet high and of uniform horizontal sectional area the variation in height of the oil between the extremes of operating conditions would be about 13 inches. With insulating bushings having shanks of standard length, such variation in oil level makes it extremely difficult to maintain the lower bushing terminals immersed in oil and at the same time retain sufficient amount of gas above the oil to properly cushion the effect of any internal explosion within the transformer.

It is, therefore, an object of this invention to provide a construction which obviates the above difficulties.

It is also an object of this invention to provide a casing with an enlarged upper portion adapted to reduce the variation in level of the liquid within the casing.

Another object of the invention is to provide both a gas expansion compartment and a liquid expansion compartment for a transformer having a gas space above the liquid in the transformer tank.

A further object of the invention is to provide a transformer casing structure having an overhanging upper portion upon which an expansion tank may be supported so that the cover of the casing may be removed without disturbing the expansion tank.

These and other objects and advantages are attained by this invention, various novel features of which will be apparent from the description and drawing herein, and will be more particularly pointed out in the claims.

An illustrative example of the application of this invention is shown in the accompanying drawing in which:

Fig. 1 is a vertical view partly in section of the upper part of a transformer embodying the present invention.

1932,, Serial No. 636,290

Fig. 2 is a fragmentary top view of Fig. I withthe insulating bushing removed.

In the drawing 8 is the lower portion of a transformer casing which is provided with a plurality of vertically disposed radiators 9 which are attached to the upper and lower ends of the casing by means of conduits 11 and radiator valves 12. The transformer casing contains a body of insulating oil 13 of suflicient quantity to substantially fill the lower portion 8 of the casing when the temperature of the oil is the lowest encountered in operation. An overhanging portion 14 of the casing is welded or otherwise attached to the lower portion 8 and comprises annular plate members 15 and 16 and a cylindrical member 1'7. A plurality of vertical ribs 18 are spaced around the periphery of the overhanging portion and are welded or otherwise attached to annular members 15 and 16 for the purpose of strengthening the overhanging portion. A plurality of brackets- 19 also support the overhanging portion and are preferably located directly beneath the respective ribs 18. A plurality of lifting lugs 21 are spaced around the periphery of the overhanging portion and are welded both to the overhanging and to the lower portion 8 of the casing. A flanged ring member 22 is welded to the upper annular member 16 and is adapted to have a cover member 23 clamped thereto by any suitable means.

Cover member 23 is provided with one or more bushing supporting rings 24, noting that only one of such rings is shown in Fig. 1 in order that other features of the invention may be more clearly illustrated. An insulating bushing 25 is suitably mounted on supporting ring 24 and is provided with an upper terminal 26 and a lower terminal 27, noting that shank portion 28 of the bushing extends through the supporting ring into the space above the oil within the transformer casing. The quantity of oil within the transformer casing is such that the lower terminal 27 is immersed in insulating oil 13 even when the oil has an ambient temperature with respect to the lowest temperature encountered during the operation of the transformer. During the normal operation of the transformer the level of the oil will rise and fall within the overhanging portion of the casing.

A pair of relief conduits 29 and 30 have their lower ends welded or otherwise attached to annular plate member 16. The upper ends of conduits 29 and 30 are provided with hinged covers 31 and 32 which are held in place by breakable bolts. A gas expansion tank 33 is mounted on relief conduits 29 and 30 which preferably extend completely through the side walls of the expansion tank. Each relief conduit is preferably provided with a detachable flanged connection below the gas expansion tank in order that this tank may be removed. Gas expansion tank 33 is provided with a vertical partitionfi l which divides the expansion tank into two compartments.v The expansion tank 33 contains a sealing liquid 35 which is in communication with both compartments through an opening in the lower part of partition member 34. Relief conduit 30 is provided with a hole 36 near the upper end thereof so as to provide a communicating passageway from the gas space above the oil in the main casing to the space above the sealing liquid in the right hand compartment only. The left hand compartment of the expansion tank 33 may be provided with a unidirectional breather 3.7 and an outlet vent 38 which serve to carry to the atmosphere any moisture in the air space above the sealing liquid in the left hand compartment. An oil gage 39 is shown mounted on expansion tank 33 for the purpose of indicating the. level of the liquid seal.

The space above the oilin the lower portion 8 of the transformer casing is preferably filled with an inert gas, such as nitrogen, which is in communication with the space above the liquid in the right hand compartment of gas expansion tank 33 through hole 36 in relief conduit 30. The levels of the sealing liquid in the gas expansion tank 33 as shown in Fig. 1 correspond to the condition A wherein the oil 13 in the main casing is atminimum temperature.

Upon increase of temperature of the oil in the main casing Sthe level of the oil will rise and oil will-flow into the over hanging compartment, thereby'forcing a portion of the gas from the gas space in the main casing causing the level of the liquid seal in the left hand portion to rise. It. is thus seen that the level ofv the oil in the casing will rise at'a. rate which is less than the rate at which the volume of oil increases. This feature makes it possible to maintain sufficient gas in the space above the oil in the main casing to adequately cushion the eifects of any explosion within the. transformer, to reduce the overall height of the transformer and to maintainthe lower terminal of the bushing always immersed in insulating oil. It is to be understood that the expansion chamber into which the transformer oil flows upon expansion may have other shapes than that herein illustrated, for example, the upper portion of the casing may have a horizontal cross-sectional area which progressively increases.

Although the invention is shown as applied to a transformer which is cooled by means of. radiators, it is to be, understood that the invention is also applicable to transformers which are cooled by other means, such, for example, by means or immersed cooling coils through which a cooling fluid is circulated.

It is to be understood that the disclosure herein described is merely illustrative of the invention and is not to be taken in a limitingsense, changes in details of construction and arrangement of parts being permissible so long as within the spirit of the invention and the scope of the claims which follow.

It is claimed and desired to secure by Letters Patent:

1. In combination, a casing enclosing liquidimmersed electrical apparatus, said casing having a cover and having an upper portion of greater horizontal sectional area than the lower portion thereof, a body of expansible liquid of such volume at an ambient temperature as to fill only said lower portion and to flow into said enlarged portion when the temperature thereof rises, an insulating bushing mounted on said cover and having a lower terminal member extending into said lowerportion so as to be continually immersed in said liquid. e

2. In combination, a casing enclosing liquidimmersed electrical apparatus, said casing having a cover member, said casing having a gas space therein above the level of the liquid therein, an insulating bushing mounted on said cover member and having a terminal member extending into the liquid-within the casing when said liquid has an ambient temperature, said tank having an upper portion of greater sectional area than the lower portion thereof and-arranged above the level of said liquid at ambient temperatures so .1

that the level of said liquid rises upon increase of the temperature thereof proportionately less than the increase in volume of said liquid so as to continually maintain said terminal member immersed in said liquid.

3. In combination, a casing for electrical apparatus, said casing having an upper portion of greater cross-sectional area than the lower por tion thereof and having a removable cover member attached to said upper portion, an insulating bushing mounted on said cover member and having a terminal extending downwardly within said casing to a point. substantially levelwith the junction between said upper and said lower portions, a body of liquid partially filling said casing so that said terminal remains continually immersed in said liquid during expansion and contractioniof said liquid and a cushionof gas within said casing above the level of said liquid.

4. In combination, a transformer casing having a lower portion of substantially uniform horizontal sectional area and an upper portion of greater horizontal sectional area, said casing having a cover member, a body of liquid within said casing, a gas space above the level of said liquid, and an insulating, bushing projecting, through said cover and having a lower terminal:

immersed in said liquid, the hot liquid level of said liquid, being within said upper portion and the cold level of said liquid being within said lower portion whereby said terminal remains unexposed to said gas during the contraction of said liquid. 7

5. In combination, a transformer having a casing comprising a lower portion, an upper portion overhanging said lower portion and a cover member, an insulating bushing mounted on said cover member and provided with a terminal depending into the lower portion of said casing,

21. body of oil completely filling the lower portion of said casing and partially filling said overhanging portion upon expansion thereof, and a body of gas within said casing above the level of said liquid, the horizontal sectional area. of said upper portion ofsaid casing being so proportioned relative to the horizontal sectional area ofsaid lower portion that said terminal remains unexposed to said gas upon contraction of' said liquid.

6. In combination, a casing for electrical api'iii paratus, said casing having a lower portion and an upper portion of greater horizontal sectional area than said lower portion and having a removable cover member attached to said upper portion, a body of liquid partially filling said casing, a cushion of inert gas within said caslng above the level of said liquid, an insulating bushing extending through said cover and having a lower terminal continually immersed in said liquid, and a gas expansion tank mounted on said upper portion independent of said cover, said gas expansion tank having a chamber in communication with said cushion of inert gas.

7. In combination, a casing enclosing liquidimmersed electrical apparatus, said casing comprising a lower portion containing a body of expansible liquid, an upper portion of greater horizontal sectional area than said lower portion and containing an inert gas above the level of said liquid, and also comprising a cover member mounted on said upper portion, an insulating bushing mounted on said cover and having a lower terminal immersed in said liquid, said upper portion constituting a liquid expansion chamber wherein the level of said liquid rises and falls proportionately less than the increase and decrease of volume of said liquid, and an inert gas expansion tank supported from said upper portion and having one chamber in communication with said inert gas.

8. In combination, a casing for liquid-immersed electrical apparatus, a body of liquid partially filling said casing leaving a gas space above the level of said liquid, means providing an expan- 3 sion chamber for said liquid, and means providing an expansion chamber external of said casing for the gas above said liquid.

9. In combination, a casing for liquid-immersed electrical apparatus, a body of liquid partially filling said casing, a body of inert gas within said casing above the level of said liquid, said casing comprising a lower portion and an upper portion of larger horizontal sectional area than said lower portion, said upper portion providing a chamber for the expansion of said liquid whereby the overall height of the transformer may be reduced, and an expansion tank mounted on said casing providing an expansion chamber for said inert gas.

10. In combination, a casing for liquid-immersed electrical apparatus, a body of liquid partially filling said casing, a body of inert gas within said casing above the level of said liquid, said casing comprising a lower portion and an upper portion of larger horizontal sectional area than said lower portion, said upper portion providing a chamber for the expansion of said liquid whereby the overall height of the transformer may be reduced, an inert gas expansion tank comprising two compartments with a communicating liquid seal therebetween, and a relief conduit passing through each of said compartments and in communication with said body of inert gas, one of said conduits having an opening therein for the passage of inert gas to and from one of said compartments.

LOUIS C. NICHOLS. 

